The long-term reliability of photovoltaic modules is crucial to ensure the technical and economic viability of PV as a successful energy source. The analysis of degradation mechanisms of PV modules is key to ensure current lifetimes exceeding 25 years. This paper presents the results of the investigations carried out on the degradation mechanisms of a crystalline silicon PV installation of 2 kWp after 12 years of exposure in Málaga, Spain. The analysis was conducted by visual inspection, infrared thermography and electrical performance evaluation. By visual inspection, the most relevant defects in the modules were identified and ranked according to their frequency. The electrical performance was assessed by comparing the characteristic parameters of the individual modules, obtained by outdoor measurements at the start and end of the exposure period. The correlation of the visual defects and the shifts in the electrical parameters was analysed. The results presented show that glass weathering, delamination at the cell-EVA interface and oxidation of the antireflective coating and the cell metallization grid were the most frequently occurring defects found. The total peak power loss, including the initial light induced degradation, was 11.5%, which corresponded almost totally to a loss in short-circuit current.

We propose a new method for calculating total energies of systems of interacting electrons, which requires little more computational resources than standard density-functional theories. The total energy is calculated within the framework of many-body perturbation theory by using an efficient model of the self-energy, that nevertheless retains the main features of the exact operator. The method shows promising performance when tested against quantum Monte Carlo results for the linear response of the homogeneous electron gas and structural properties of bulk silicon.

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In this paper, the results of the analysis of the degradation of a set of single-crystalline silicon modules after 21 years are presented. The comparison of the main electrical parameters and the series and of the shunt resistances measured in 1996 and 2017 is performed, so that the annual degradation rate is evaluated. In addition, a detailed analysis of the parameter uncertainties has been performed in order to determine its impact on the results. A visual inspection of the modules has also been carried out in order to show the correlation with the variation of the electrical performance.Finally, the temperature coefficients of the degraded modules have been estimated and compared with the nominal ones. The results shown in the paper reveal that the mean annual degradation rate in terms of power is close to 0.9%. KEYWORDSI-V curve correction, outdoor measurement, photovoltaic degradation, temperature coefficient, uncertainty analysis, visual defect main electrical parameters and the increase in their dispersion have to be considered. As each module tends to degrade in a different way, the behavior of the modules will be more and more different as time goes by, thus affecting negatively the global performance of the plant.According to Köntges et al. 2 a module defect is an irreversible damage that causes either a degradation in terms of power or a security risk. These defects can be classified in different categories wileyonlinelibrary.com/journal/pip

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